Thiazole compounds, compositions and methods for treatment of degenerative diseases and disorders

ABSTRACT

Provided herein are compounds of the formula (I): 
                         
as well as pharmaceutically acceptable salts thereof, wherein the substituents are as those disclosed in the specification. These compounds, and the pharmaceutical compositions containing them, are useful for the treatment of degenerative diseases and disorders.

This application claims priority to and is a continuation of ending U.S. patent application Ser. No. 13/798,421, filed Mar. 13, 2013, incorporated by references herein.

FIELD OF THE INVENTION

The invention is directed to compounds of formula (I):

and to pharmaceutical compositions comprising the compounds. The compounds and compositions disclosed herein protect against calcium- and oxidative-stress mediated damage to mitochondrial function and are useful for the treatment of degenerative diseases and disorders.

All documents cited or relied upon below are expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

Mitochondria are cellular organelles present in most eukaryotic cells. One of their primary functions is oxidative phosphorylation, a process through which energy derived from metabolism of fuels like glucose or fatty acids is converted to ATP, which is then used to drive various energy-requiring biosynthetic reactions and other metabolic activities. Mitochondria have their own genomes, separate from nuclear DNA, comprising rings of DNA with about 16,000 base pairs in human cells. Each mitochondrion may have multiple copies of its genome, and individual cells may have hundreds of mitochondria. In addition to supplying cellular energy, mitochondria are involved in a range of other processes, such as signaling, cellular differentiation, cell death, as well as the control of the cell cycle and cell growth (McBride et al., Curr. Biol., 2006, 16 (14): R551).

As mitochondria produce ATP, they simultaneously yield reactive oxygen species (ROS), which are harmful free radicals that circulate throughout the cell, the mitochondria, and the body, causing more damage. The circulation of ROS leads to the activation of reactive nitrogen compounds, which in turn induce, or activate, genes in the DNA that are associated with many degenerative diseases. The DNA for each mitochondrion (mtDNA) remains unprotected within the membrane of the mitochondrion itself. In comparison to the DNA in the nucleus of the cell (nDNA), mtDNA is easily damaged by free radicals and the ROS that it produces. Freely floating mtDNA lacks protective measures associated with nDNA, and therefore suffers from multiple mutations. It has been estimated that the lack of protective measures results in mutations to mtDNA occurring 10 to 20 times more frequently than mutations to nDNA.

Mitochondrial damage and/or dysfunction contribute to various disease states. Some diseases are due to mutations or deletions in the mitochondrial genome. Mitochondria divide and proliferate with a faster turnover rate than their host cells, and their replication is under control of the nuclear genome. If a threshold proportion of mitochondria in a cell is defective, and if a threshold proportion of such cells within a tissue have defective mitochondria, symptoms of tissue or organ dysfunction can result. Practically any tissue can be affected, and a large variety of symptoms can be present, depending on the extent to which different tissues are involved.

A fertilized ovum might contain both normal and genetically defective mitochondria. The segregation of defective mitochondria into different tissues during division of this ovum is a stochastic process, as will be the ratio of defective to normal mitochondria within a given tissue or cell (although there can be positive or negative selection for defective mitochondrial genomes during mitochondrial turnover within cells). Thus, a variety of different pathologic phenotypes can emerge out of a particular point mutation in mitochondrial DNA. Conversely, similar phenotypes can emerge from mutations or deletions affecting different genes within mitochondrial DNA. Clinical symptoms in congenital mitochondrial diseases often manifest in postmitotic tissues with high energy demands like brain, muscle, optic nerve, and myocardium, but other tissues including endocrine glands, liver, gastrointestinal tract, kidney, and hematopoietic tissue are also involved, again depending in part on the segregation of mitochondria during development, and on the dynamics of mitochondrial turnover over time.

In addition to congenital disorders involving inherited defective mitochondria, acquired mitochondrial damage and/or dysfunction contribute to diseases, particularly neurodegenerative disorders associated with aging like Parkinson's, Alzheimer's, Huntington's Diseases. The incidence of somatic mutations in mitochondrial DNA rises exponentially with age; and diminished respiratory chain activity is found universally in aging people. Mitochondrial dysfunction is also implicated in excitotoxic neuronal injury, such as that associated with seizures or ischemia.

Other pathologies with etiology involving mitochondrial damage and/or dysfunction include schizophrenia, bipolar disorder, dementia, epilepsy, stroke, cardiovascular disease, retinal degenerative disease (e.g., age-related macular degeneration, Stargardt's disease, glaucoma, retinitis pigmentosa, and optic nerve degeneration), and diabetes mellitus. A common thread thought to link these seemingly-unrelated conditions is cellular damage causing oxidative stress. Oxidative stress is caused by an imbalance between the production of reactive oxygen and a biological system's ability to readily detoxify the reactive intermediates or easily repair the resulting damage. All forms of life maintain a reducing environment within their cells. This reducing environment is preserved by enzymes that maintain the reduced state through a constant input of metabolic energy. Disturbances in this normal redox state can cause toxic effects through the production of peroxides and free radicals that damage all components of the cell, including proteins, lipids, and DNA.

Mitochondrial damage and/or dysfunction particularly contribute to degenerative diseases. Degenerative diseases are diseases in which the function or structure of the affected tissues or organs will progressively deteriorate over time. Some examples of degenerative diseases are retinal degenerative disease, e.g., age-related macular degeneration, Stargardt's disease, glaucoma, retinitis pigmentosa, and optic nerve degeneration; amyotrophic lateral sclerosis (ALS), e.g., Lou Gehrig's disease; Alzheimer's disease; Parkinson's disease; multiple system atrophy; Niemann Pick disease; atherosclerosis; progressive supranuclear palsy; cancer; Tay-Sachs disease; diabetes; heart disease; keratoconus; inflammatory bowel disease (IBD); prostatitis; osteoarthritis; osteoporosis; rheumatoid arthritis; and Huntington's disease.

Treatment of degenerative diseases involving mitochondrial damage and/or dysfunction has heretofore involved administration of vitamins and cofactors used by particular elements of the mitochondrial respiratory chain. Coenzyme Q (ubiquinone), nicotinamide, riboflavin, carnitine, biotin, and lipoic acid are used in patients with occasional benefit, especially in disorders directly stemming from primary deficiencies of one of these cofactors. However, while useful in isolated cases, no such metabolic cofactors or vitamins have been shown to have general utility in clinical practice in treating degenerative diseases involving mitochondrial damage and/or dysfunction.

Therefore, a need exists for new drug therapies for the treatment of subjects suffering from or susceptible to the above disorders or conditions associated with mitochondrial damage and/or dysfunction. In particular, a need exists for new drugs having one or more improved properties (such as safety profile, efficacy or physical properties) relative to those currently available.

SUMMARY OF THE INVENTION

The present invention is directed to compounds according to formula (I):

wherein:

R₁ is pyridinyl or phenyl;

R₂ is pyridinyl, unsubstituted phenyl or phenyl substituted with alkoxy;

R₃ is —OR₄ or —NR₅R₆;

R₄ is hydrogen or lower alkyl; and

one of R₅ or R₆ is hydrogen or methyl and the other is unsubstituted lower alkyl, unsubstituted phenyl, lower alkyl substituted with alkoxy or phenyl substituted with halogen, alkoxy or —NH-phenyl;

or a pharmaceutically acceptable salt thereof.

The present invention is also directed to pharmaceutical compositions containing the above compounds, method of using the compounds and to methods of treating degenerative diseases and disorders.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the terminology employed herein is for the purpose of describing particular embodiments, and is not intended to be limiting. Further, although any methods, devices and materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices and materials are now described.

As used herein, the term “alkyl”, alone or in combination with other groups, refers to a branched or straight-chain monovalent saturated aliphatic hydrocarbon radical of one to twenty carbon atoms, preferably one to sixteen carbon atoms, more preferably one to ten carbon atoms.

As used herein, the term “alkenyl”, alone or in combination with other groups, refers to a straight-chain or branched hydrocarbon residue having an olefinic bond.

The term “cycloalkyl” refers to a monovalent mono- or polycarbocyclic radical of three to ten, preferably three to six carbon atoms. This term is further exemplified by radicals such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, norbornyl, adamantyl, indanyl and the like. In a preferred embodiment, the “cycloalkyl” moieties can optionally be substituted with one, two, three or four substituents. Each substituent can independently be, alkyl, alkoxy, halogen, amino, hydroxyl or oxygen (O.dbd.) unless otherwise specifically indicated. Examples of cycloalkyl moieties include, but are not limited to, optionally substituted cyclopropyl, optionally substituted cyclobutyl, optionally substituted cyclopentyl, optionally substituted cyclopentenyl, optionally substituted cyclohexyl, optionally substituted cyclohexylene, optionally substituted cycloheptyl, and the like or those which are specifically exemplified herein.

The term “heterocycloalkyl” denotes a mono- or polycyclic alkyl ring, wherein one, two or three of the carbon ring atoms is replaced by a heteroatom such as N, O or S. Examples of heterocycloalkyl groups include, but are not limited to, morpholinyl, thiomorpholinyl, piperazinyl, piperidinyl, pyrrolidinyl, tetrahydropyranyl, tetrahydrofuranyl, 1,3-dioxanyl and the like. The heterocycloalkyl groups may be unsubstituted or substituted and attachment may be through their carbon frame or through their heteroatom(s) where appropriate.

The term “lower alkyl”, alone or in combination with other groups, refers to a branched or straight-chain alkyl radical of one to nine carbon atoms, preferably one to six carbon atoms, more preferably one to four carbon atoms. This term is further exemplified by radicals such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, n-pentyl, 3-methylbutyl, n-hexyl, 2-ethylbutyl and the like.

The term “aryl” refers to an aromatic mono- or polycarbocyclic radical of 6 to 12 carbon atoms having at least one aromatic ring. Examples of such groups include, but are not limited to, phenyl, naphthyl, 1,2,3,4-tetrahydronaphthalene, 1,2-dihydronaphthalene, indanyl, 1H-indenyl and the like.

The alkyl, lower alkyl and aryl groups may be substituted or unsubstituted. When substituted, there will generally be, for example, 1 to 4 substituents present. These substituents may optionally form a ring with the alkyl, lower alkyl or aryl group with which they are connected. Substituents may include, for example: carbon-containing groups such as alkyl, aryl, arylalkyl (e.g. substituted and unsubstituted phenyl, substituted and unsubstituted benzyl); halogen atoms and halogen-containing groups such as haloalkyl (e.g. trifluoromethyl); oxygen-containing groups such as alcohols (e.g. hydroxyl, hydroxyalkyl, aryl(hydroxyl)alkyl), ethers (e.g. alkoxy, aryloxy, alkoxyalkyl, aryloxyalkyl, more preferably, for example, methoxy and ethoxy), aldehydes (e.g. carboxaldehyde), ketones (e.g. alkylcarbonyl, alkylcarbonylalkyl, arylcarbonyl, arylalkylcarbonyl, arycarbonylalkyl), acids (e.g. carboxy, carboxyalkyl), acid derivatives such as esters (e.g. alkoxycarbonyl, alkoxycarbonylalkyl, alkylcarbonyloxy, alkylcarbonyloxyalkyl), amides (e.g. aminocarbonyl, mono- or di-alkylaminocarbonyl, aminocarbonylalkyl, mono- or di-alkylaminocarbonylalkyl, arylaminocarbonyl), carbamates (e.g. alkoxycarbonylamino, aryloxycarbonylamino, aminocarbonyloxy, mono- or di-alkylaminocarbonyloxy, arylminocarbonloxy) and ureas (e.g. mono- or di-alkylaminocarbonylamino or arylaminocarbonylamino); nitrogen-containing groups such as amines (e.g. amino, mono- or di-alkylamino, aminoalkyl, mono- or di-alkylaminoalkyl), azides, nitriles (e.g. cyano, cyanoalkyl), nitro; sulfur-containing groups such as thiols, thioethers, sulfoxides and sulfones (e.g. alkylthio, alkylsulfinyl, alkylsulfonyl, alkylthioalkyl, alkylsulfinylalkyl, alkylsulfonylalkyl, arylthio, arysulfinyl, arysulfonyl, arythioalkyl, arylsulfinylalkyl, arylsulfonylalkyl); and heterocyclic groups containing one or more heteroatoms, (e.g. thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, thiadiazolyl, aziridinyl, azetidinyl, pyrrolidinyl, pyrrolinyl, imidazolidinyl, imidazolinyl, pyrazolidinyl, tetrahydrofuranyl, pyranyl, pyronyl, pyridyl, pyrazinyl, pyridazinyl, piperidyl, hexahydroazepinyl, piperazinyl, morpholinyl, thianaphthyl, benzofuranyl, isobenzofuranyl, indolyl, oxyindolyl, isoindolyl, indazolyl, indolinyl, 7-azaindolyl, benzopyranyl, coumarinyl, isocoumarinyl, quinolinyl, isoquinolinyl, naphthridinyl, cinnolinyl, quinazolinyl, pyridopyridyl, benzoxazinyl, quinoxalinyl, chromenyl, chromanyl, isochromanyl, phthalazinyl and carbolinyl).

The term “heteroaryl,” refers to an aromatic mono- or polycyclic radical of 5 to 12 atoms having at least one aromatic ring containing one, two, or three ring heteroatoms selected from N, O, and S, with the remaining ring atoms being C. One or two ring carbon atoms of the heteroaryl group may be replaced with a carbonyl group.

The heteroaryl group described above may be substituted independently with one, two, or three substituents. Substituents may include, for example: carbon-containing groups such as alkyl, aryl, arylalkyl (e.g. substituted and unsubstituted phenyl, substituted and unsubstituted benzyl); halogen atoms and halogen-containing groups such as haloalkyl (e.g. trifluoromethyl); oxygen-containing groups such as alcohols (e.g. hydroxyl, hydroxyalkyl, aryl(hydroxyl)alkyl), ethers (e.g. alkoxy, aryloxy, alkoxyalkyl, aryloxyalkyl), aldehydes (e.g. carboxaldehyde), ketones (e.g. alkylcarbonyl, alkylcarbonylalkyl, arylcarbonyl, arylalkylcarbonyl, arycarbonylalkyl), acids (e.g. carboxy, carboxyalkyl), acid derivatives such as esters (e.g. alkoxycarbonyl, alkoxycarbonylalkyl, alkylcarbonyloxy, alkylcarbonyloxyalkyl), amides (e.g. aminocarbonyl, mono- or di-alkylaminocarbonyl, aminocarbonylalkyl, mono- or di-alkylaminocarbonylalkyl, arylaminocarbonyl), carbamates (e.g. alkoxycarbonylamino, aryloxycarbonylamino, aminocarbonyloxy, mono- or di-alkylaminocarbonyloxy, arylminocarbonloxy) and ureas (e.g. mono- or di-alkylaminocarbonylamino or arylaminocarbonylamino); nitrogen-containing groups such as amines (e.g. amino, mono- or di-alkylamino, aminoalkyl, mono- or di-alkylaminoalkyl), azides, nitriles (e.g. cyano, cyanoalkyl), nitro; sulfur-containing groups such as thiols, thioethers, sulfoxides and sulfones (e.g. alkylthio, alkylsulfinyl, alkylsulfonyl, alkylthioalkyl, alkylsulfinylalkyl, alkylsulfonylalkyl, arylthio, arysulfinyl, arysulfonyl, arythioalkyl, arylsulfinylalkyl, arylsulfonylalkyl); and heterocyclic groups containing one or more heteroatoms, (e.g. thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, thiadiazolyl, aziridinyl, azetidinyl, pyrrolidinyl, pyrrolinyl, imidazolidinyl, imidazolinyl, pyrazolidinyl, tetrahydrofuranyl, pyranyl, pyronyl, pyridyl, pyrazinyl, pyridazinyl, piperidyl, hexahydroazepinyl, piperazinyl, morpholinyl, thianaphthyl, benzofuranyl, isobenzofuranyl, indolyl, oxyindolyl, isoindolyl, indazolyl, indolinyl, 7-azaindolyl, benzopyranyl, coumarinyl, isocoumarinyl, quinolinyl, isoquinolinyl, naphthridinyl, cinnolinyl, quinazolinyl, pyridopyridyl, benzoxazinyl, quinoxalinyl, chromenyl, chromanyl, isochromanyl, phthalazinyl, benzothiazoyl and carbolinyl).

As used herein, the term “alkoxy” means alkyl-O—; and “alkoyl” means alkyl-CO—. Alkoxy substituent groups or alkoxy-containing substituent groups may be substituted by, for example, one or more alkyl groups.

As used herein, the term “halogen” means a fluorine, chlorine, bromine or iodine radical, preferably a fluorine, chlorine or bromine radical, and more preferably a bromine or chlorine radical.

Compounds of formula I can have one or more asymmetric carbon atoms and can exist in the form of optically pure enantiomers, mixtures of enantiomers such as, for example, racemates, optically pure diastereoisomers, mixtures of diastereoisomers, diastereoisomeric racemates or mixtures of diastereoisomeric racemates. The optically active forms can be obtained for example by resolution of the racemates, by asymmetric synthesis or asymmetric chromatography (chromatography with a chiral adsorbents or eluant). The invention embraces all of these forms.

As used herein, the term “pharmaceutically acceptable salt” means any pharmaceutically acceptable salt of the compound of formula (I). Salts may be prepared from pharmaceutically acceptable non-toxic acids and bases including inorganic and organic acids and bases. Such acids include, for example, acetic, benzenesulfonic, benzoic, camphorsulfonic, citric, ethenesulfonic, dichloroacetic, formic, fumaric, gluconic, glutamic, hippuric, hydrobromic, hydrochloric, isethionic, lactic, maleic, malic, mandelic, methanesulfonic, mucic, nitric, oxalic, pamoic, pantothenic, phosphoric, succinic, sulfuric, tartaric, oxalic, p-toluenesulfonic and the like. Particularly preferred are fumaric, hydrochloric, hydrobromic, phosphoric, succinic, sulfuric and methanesulfonic acids. Acceptable base salts include alkali metal (e.g. sodium, potassium), alkaline earth metal (e.g. calcium, magnesium) and aluminum salts.

In one embodiment of the invention, provided is a compound of formula (I):

wherein:

R₁ is pyridinyl or phenyl;

R₂ is pyridinyl, unsubstituted phenyl or phenyl substituted with alkoxy;

R₃ is —OR₄ or —NR₅R₆;

R₄ is hydrogen or lower alkyl; and

one of R₅ or R₆ is hydrogen or methyl and the other is unsubstituted lower alkyl, unsubstituted phenyl, lower alkyl substituted with alkoxy or phenyl substituted with halogen, alkoxy or —NH-phenyl;

or a pharmaceutically acceptable salt thereof.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₁ is pyridinyl.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₁ is or phenyl.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₂ is pyridinyl.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₂ is unsubstituted phenyl or phenyl substituted with alkoxy.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₃ is —OR₄.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₃ is —NR₅R₆.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₄ is hydrogen or ethyl.

In another embodiment of the invention, provided is a compound of formula (I), wherein one of R₅ or R₆ is hydrogen and the other is unsubstituted lower alkyl, unsubstituted phenyl, lower alkyl substituted with alkoxy or phenyl substituted with halogen, alkoxy or —NH-phenyl.

In another embodiment of the invention, provided is a compound of formula (I), wherein one of R₅ or R₆ is lower alkyl and the other is unsubstituted lower alkyl, unsubstituted phenyl, lower alkyl substituted with alkoxy or phenyl substituted with halogen, alkoxy or —NH-phenyl.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₃ is hydroxy or alkoxy.

In another embodiment of the invention, provided is a compound of formula (I), wherein R₃ is —NH-phenyl, —NH-halophenyl, —N(CH₃)CH₂CH₂OCH₃, —NH-phenylalkoxy or —NH-phenylaminophenyl.

In another embodiment of the invention, provided is a compound of formula (I), wherein the compound is:

Ethyl 2,4-diphenylthiazole-5-carboxylate;

2,4-diphenylthiazole-5-carboxylic acid;

N,2,4-triphenylthiazole-5-carboxamide;

N-(4-fluorophenyl)-2,4-diphenylthiazole-5-carboxamide;

Ethyl 2-(4-methoxyphenyl)-4-phenylthiazole-5-carboxylate;

N-(2-methoxyethyl)-N-methyl-2,4-diphenylthiazole-5-carboxamide;

Ethyl 4-phenyl-2-(pyridin-2-yl)thiazole-5-carboxylate;

N-(4-methoxyphenyl)-2,4-diphenylthiazole-5-carboxamide;

Ethyl 2-phenyl-4-(pyridin-2-yl)thiazole-5-carboxylate;

Ethyl 4-phenyl-2-(pyridin-4-yl)thiazole-5-carboxylate;

4-Phenyl-2-(pyridin-2-yl)thiazole-5-carboxylic acid; or

4-Phenyl-N-(2-(phenylamino)phenyl)-2-(pyridin-2-yl)thiazole-5-carboxamide.

In a further embodiment of the invention, provided is a pharmaceutical composition, comprising a therapeutically effective amount of a compound according to formula (I) or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier.

In a further embodiment of the invention, provided is a method for treating a degenerative disease or disorder, comprising the step of administering a therapeutically effective amount of a compound according to formula (I) or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier to a patient in need thereof. The degenerative diseases and disorders include, for example retinitis pigmentosa.

In another embodiment of the invention, provided is a method of treating a retinal degenerative disease in a subject in need thereof, comprising administering to said subject a therapeutically effective amount of a compound or a pharmaceutically acceptable salt thereof according to formula (I).

In a yet further embodiment of the invention, provided is a method for preventing calcium-induced or oxidant-induced mitochondrial damage preventing or loss of mitochondrial respiratory capacity in a cell susceptible thereof wherein the calcium-induced or oxidant-induced mitochondrial damage or loss of mitochondrial respiratory capacity comprises excess of cGMP that increases the number of cGMP-gated cation channels in an open configuration, allowing an influx of Ca2+ into the cell, said method comprising contacting the cell with an effective amount of a compound or a pharmaceutically acceptable salt thereof according to formula (I).

In the practice of the method of the present invention, an effective amount of any one of the compounds of this invention or a combination of any of the compounds of this invention or a pharmaceutically acceptable salt thereof, is administered via any of the usual and acceptable methods known in the art, either singly or in combination. The compounds or compositions can thus be administered, for example, ocularly, orally (e.g., buccal cavity), sublingually, parenterally (e.g., intramuscularly, intravenously, or subcutaneously), rectally (e.g., by suppositories or washings), transdermally (e.g., skin electroporation) or by inhalation (e.g., by aerosol), and in the form or solid, liquid or gaseous dosages, including tablets and suspensions. The administration can be conducted in a single unit dosage form with continuous therapy or in a single dose therapy ad libitum. The therapeutic composition can also be in the form of an oil emulsion or dispersion in conjunction with a lipophilic salt such as pamoic acid, or in the form of a biodegradable sustained-release composition for subcutaneous or intramuscular administration.

Useful pharmaceutical carriers for the preparation of the compositions hereof, can be solids, liquids or gases. Thus, the compositions can take the form of tablets, pills, capsules, suppositories, powders, enterically coated or other protected formulations (e.g. binding on ion-exchange resins or packaging in lipid-protein vesicles), sustained release formulations, solutions, suspensions, elixirs, aerosols, and the like. The carrier can be selected from the various oils including those of petroleum, animal, vegetable or synthetic origin, e.g., peanut oil, soybean oil, mineral oil, sesame oil, and the like. Water, saline, aqueous dextrose, and glycols are preferred liquid carriers, particularly (when isotonic with the blood) for injectable solutions. For example, formulations for intravenous administration comprise sterile aqueous solutions of the active ingredient(s) which are prepared by dissolving solid active ingredient(s) in water to produce an aqueous solution, and rendering the solution sterile. Suitable pharmaceutical excipients include starch, cellulose, talc, glucose, lactose, talc, gelatin, malt, rice, flour, chalk, silica, magnesium stearate, sodium stearate, glycerol monostearate, sodium chloride, dried skim milk, glycerol, propylene glycol, water, ethanol, and the like. The compositions may be subjected to conventional pharmaceutical additives such as preservatives, stabilizing agents, wetting or emulsifying agents, salts for adjusting osmotic pressure, buffers and the like. Suitable pharmaceutical carriers and their formulation are described in Remington's Pharmaceutical Sciences by E. W. Martin. Such compositions will, in any event, contain an effective amount of the active compound together with a suitable carrier so as to prepare the proper dosage form for proper administration to the recipient.

The dose of a compound of the present invention depends on a number of factors, such as, for example, the manner of administration, the age and the body weight of the subject, and the condition of the subject to be treated, and ultimately will be decided by the attending physician or veterinarian. Such an amount of the active compound as determined by the attending physician or veterinarian is referred to herein, and in the claims, as a “therapeutically effective amount”. For example, the dose of a compound of the present invention is typically in the range of about 1 to about 1000 mg per day. Preferably, the therapeutically effective amount is in an amount of from about 1 mg to about 500 mg per day.

It will be appreciated, that the compounds of general formula I in this invention may be derivatized at functional groups to provide derivatives which are capable of conversion back to the parent compound in vivo. Physiologically acceptable and metabolically labile derivatives, which are capable of producing the parent compounds of general formula I in vivo are also within the scope of this invention.

Compounds of the present invention can be prepared beginning with commercially available starting materials and utilizing general synthetic techniques and procedures known to those skilled in the art. Chemicals may be purchased from companies such as for example Aldrich, Argonaut Technologies, VWR and Lancaster. Chromatography supplies and equipment may be purchased from such companies as for example AnaLogix, Inc, Burlington, Wis.; Biotage AB, Charlottesville, Va.; Analytical Sales and Services, Inc., Pompton Plains, N.J.; Teledyne Isco, Lincoln, Nebr.; VWR International, Bridgeport, N.J.; Varian Inc., Palo Alto, Calif., and Multigram II Mettler Toledo Instrument Newark, Del. Biotage, ISCO and Analogix columns are pre-packed silica gel columns used in standard chromatography.

The compounds of formula I can be prepared according to the following scheme:

As seen in Scheme 1, compounds of formula I may be made using intermediate i. Intermediate i may be made by oxidizing commercially available ethyl 3-oxo-3-(pyridin-2-yl)propanoate, ethyl 3-oxo-3-(phenyl)propanoate or any other short alkyl chain 3-oxo-3-(aryl)propanoate using commercially available [hydroxyl(tosyloxy)]iodobenzene in a solvent like anhydrous acetonitrile to afford R₄ where R₄ is an oxytosyl at the appropriate temperature such as room temperature or 60° C. R₁ may be, for example, phenyl, 2-pyridyl, 3 pyridyl, or aryl and R₃ may be, for example, alkyl, any short chained alkyl derivative, ethyl, methyl, hydroxyl, may be either or both aryl, phenyl, 2-methoxy-ethyl, 4-methoxyphenyl, 4-fluorophenyl, 2-(phenylamino)phenyl, hydrogen, methyl, or any other short chained alkyl derivative (see Herrero, M. Teresa; Tellitu, Imanol; Dominguez, Esther; Hernandez, Susana; Moreno, Isabel; SanMartin, Raul, Tetrahedron (2002), 58(42), 8581-8589). Formation of compounds with formula I may then be done by condensation of intermediate i with a thioamide where R₂ may be, for example, aryl, phenyl, 4-methoxyphenyl, pyridin-2-yl, pyridin-4-yl in a solvent like dimethylformamide at the appropriate temperature and time period such as 60° C. for 48 hours. In instances where R₃ is formulated as an ether, hydrolysis of may occur under basic conditions such as lithium hydroxide, sodium hydroxide, or potassium hydroxide in a solvent like a methanol water mixture at the appropriate temperature to afford compounds of formula II. Compounds of formula III may be made by reacting the appropriate amine with compounds of formula II where R₃ may be, for example, a hydroxyl group to afford compounds of formula III where R₃ may be, for example, an amine tethered to either or both aryl, phenyl, 2-methoxy-ethyl, 4-methoxyphenyl, 4-fluorophenyl, 2-(phenylamino)phenyl, hydrogen, methyl, or any other short chained alkyl derivative. The condensation reaction may occur using a base like diisopropylethylamine, triethyl amine, trimethylamine, purchased from any common vendor and a reagent like 1H-Benzotiazolium 1-[bis(dimethylamino)methylene]-5chloro-hexafluorophosphate (1-),3-oxide (purchased from Peptides International) in a solvent like anhydrous dimethylformamide. An alternate procedure towards compounds of formula III would be using dicycloheximide, EDCI, EDC, or any other common coupling protocol and the appropriate amine described above in a solvent like DMF, methanol, or THF.

The invention will now be further described in the Examples below, which are intended as an illustration only and do not limit the scope of the invention.

EXAMPLES I. Preparation of Certain Intermediates of the Invention Ethyl 3-oxo-3-phenyl-2-(tosyloxy)propanoate

To a flame dried flask cooled under argon equipped with a stir bar was added [hydroxyl(tosyloxy)]iodobenzene (1.94 grams, 4.94 mmol) and 10.0 mL of anhydrous acetonitrile (purchased from Fisher Scientific). The stirring solution was then warmed to approximately 40° C. While stirring at this temperature 3-oxo-3-(phenyl)propanoate (purchased from Aldrich, 1.0 mL, 5.2 mmol) was added slowly. The reaction continued to stir at this temperature until completion. Once complete, the reaction was partitioned between dichlormethane and water. The organic layer was removed. The aqueous layer was then washed twice more with dichloromethane. The combined organic material was then dried with sodium sulfate, filtered and concentrated. Purification was done using a silica support liquid chromatography (hexane; ethyl acetate 85:15) to afford the desired compound. Yield, 90%. (Herrero, M. Teresa; Tellitu, Imanol; Dominguez, Esther; Hernandez, Susana; Moreno, Isabel; SanMartin, Raul, Tetrahedron (2002), 58(42), 8581-8589.)

Ethyl 3-oxo-3-(pyridin-2-yl)-2-(tosyloxy)propanoate

Was made in a similar fashion to ethyl 3-oxo-3-phenyl-2-(tosyloxy)propanoate using commercially available ethyl 3-oxo-3-(pyridin-2-yl)propanoate (purchased from Aldrich). 1H NMR δ 8.64 (dd, 1H), 8.02 (d, 1H), 7.88 (m, 3H), 7.52 (dd, 1H), 7.32 (d, 2H), 6.72 (s, 1H), 4.17 (d, 2H), 2.44 (s, 3H), 1.13 (t, 3H).

II. Preparation of Certain Embodiments of the Invention Example 1 Ethyl 2,4-diphenylthiazole-5-carboxylate

To a flame dried flask cooled under argon was added ethyl 3-oxo-3-phenyl-2-(tosyloxy)propanoate (0.1 grams, 0.276 mmol), benzothioamide (0.038 grams, 0.28 mmol, purchased from Aldrich) and 1 mL of DMF (anhydrous, purchased from Fisher Scientific). The stirring solution was then heated to 60° C. where the reaction remained until it had gone to completion. It was then cooled to room temperature and concentrated. Chromatography using silica gel (hexanes, ethyl acetate (95:5) afforded the desired ethyl 2,4-diphenylthiazole-5-carboxylate in 85% yield.

Example 2 2,4-Diphenylthiazole-5-carboxylic acid

To a clean flask equipped with a stir bar was added ethyl 2,4-diphenylthiazole-5-carboxylate (0.072 grams, 0.233 mmol). This was taken up in 2 mL of THF (purchased from Aldrich) and 0.25 mL of ethanol (95% purchased from Fisher Scientific). While stirring at room temperature 1.2 mL of NaOH (aqueous, 1.0M) was added and the solution heated to a reflux. After four hours of refluxing, the solution was cooled and concentrated using a Buchi rotoevaporator. It was next acidified using 1.0M HCl, and diluted with ethyl acetate. The organic layer was then extracted. The aqueous layer was washed twice with ethyl acetate. The combined organic material was next dried with sodium sulfate, filtered and concentrated. A partial recrystallization was done using ethyl acetate. It was then used for the subsequent step. Yield, 78%. 1H NMR δ 8.05 (dd, 2H), 7.85 (dd, 2H), 7.49 (m, 6H), 4.4 (bs, OH). Calculated mass for C16H11NO2S 281.05, observed 282.1 (M+1).

Example 3 N,2,4-Triphenylthiazole-5-carboxamide

To a flame dried flask cooled under argon was added 2,4-diphenylthiazole-5-carboxylic acid (0.0157 grams, 0.056 mmol), 1H-Benzotriazolium 1-[bis(dimethylamino)methylene]-5chloro-,hexafluorophosphate (1-),3-oxide (0.032 grams, 0.08 mmol, HCTU, purchased from Peptides International) and 0.5 mL of DMF (anhydrous, purchased from Fisher Scientific). After ten minutes of stirring aniline (5.4 μL, 0.059 mmol) was added followed by N,N-diisopropyl-N-ethylamine (20 μL, 0.112 mmol, anhydrous, Sure Seal, purchased from Aldrich). The reaction stirred at roomed temperature over night. The next day, the reaction was quenched with water and ethyl acetate. The organic layer was extracted. The aqueous layer was then washed twice with ethyl acetate. The combined organic material was dried with sodium sulfate, filtered and concentrated. Purification was done using a preparative thin layer chromatography on silica gel (hexanes, ethyl acetate 8:2) to afford the desired compound. 26% yield. 1H NMR δ 8.04 (m, 2H), 7.78 (m, 2H), 7.59 (m, 3H), 7.49 (m, 4H), 7.298 (m, 4H), 7.11 (t, 1H). Calculated mass for C22H16N2OS, 356.10. Observed 357.2 (M+1).

Example 4 N-(4-fluorophenyl)-2,4-diphenylthiazole-5-carboxamide

This compound was made in a similar manner to N,4-diphenyl-2-(pyridin-3-yl)thiazole-5-carboxamide using 2,4-diphenylthiazole-5-carboxylic acid and 4-fluoro-aniline (purchased from Aldrich). 1H NMR δ 8.05 (m, 2H), 7.77 (m, 2H), 7.60 (m, 3H), 7.50 (m, 4H), 7.37 (s, 1H), 7.21 (m, 2H), 6.95 (t, 1H). Calculated mass for C22H15FN2OS, 374.09. Observed 375.2 (M+1).

Example 5 Ethyl 2-(4-methoxyphenyl)-4-phenylthiazole-5-carboxylate

This compound was made in a similar manner to ethyl 2,4-diphenylthiazole-5-carboxylate using ethyl 3-oxo-3-phenyl-2-(tosyloxy)propanoate and 4-methoxy-thiobenzamide (purchased from Aldrich). 1H NMR δ 8.00 (d, 2H), 7.83 (m, 2H), 7.47 (m, 3H), 6.98 (d, 2H), 4.32 (q, 2H), 3.88 (s, 3H), 1.30 (t, 3H). Calculated mass for C19H17NO3S, 339.09. Observed 340.1 (M+1).

Example 6 N-(2-methoxyethyl)-N-methyl-2,4-diphenylthiazole-5-carboxamide

This compound was made in a similar manner to N,4-diphenyl-2-(pyridin-3-yl)thiazole-5-carboxamide using 2,4-diphenylthiazole-5-carboxylic acid and 2-methoxy-N-methylethanamine (purchased from Aldrich). 1H NMR δ 8.02 (m, 2H), 7.83 (d, 2H), 7.47 (m, 6H), 3.64 (m, 3H), 3.37 (s, 2H), 3.15 (m, 3H), 2.79 (s, 2H).

Example 7 Ethyl 4-phenyl-2-(pyridin-2-yl)thiazole-5-carboxylate

This compound was made in a similar manner to ethyl 2,4-diphenylthiazole-5-carboxylate using ethyl 3-oxo-3-phenyl-2-(tosyloxy)propanoate and pyridine-2-carbothioamide (purchased from Aldrich). 1H NMR δ 8.67 (d, 1H), 8.31 (d, 1H), 7.85 (m, 3H), 7.48 (m, 3H), 7.40 (dd, 1H), 4.32 (q, 2H), 1.33 (t, 3H).

Example 8 N-(4-methoxyphenyl)-2,4-diphenylthiazole-5-carboxamide

This compound was made in a similar manner to N,4-diphenyl-2-(pyridin-3-yl)thiazole-5-carboxamide using 2,4-diphenylthiazole-5-carboxylic acid and 4-methoxyaniline (purchased from Aldrich). 1H NMR δ 8.04 (dd, 2H), 7.78 (dd, 2H), 7.59 (m, 3H), 7.50 (m, 3H), 7.40 (bs, 1NH), 7.16 (d, 2H), 6.09 (d, 2H), 3.78 (s, 3H).

Example 9 Ethyl 2-phenyl-4-(pyridin-2-yl)thiazole-5-carboxylate

This compound was made in a similar manner to ethyl 2,4-diphenylthiazole-5-carboxylate using ethyl 3-oxo-3-(pyridin-2-yl)-2-(tosyloxy)propanoate and benzothioamide (purchased from Aldrich). 1H NMR δ 8.75 (d, 1H), 8.05 (dd, 2H), 7.82 (dd, 2H), 7.29 (m, 3H), 7.37 (dd, 1H), 4.30 (q, 2H), 1.28 (t, 3H).

Example 10 Ethyl 4-phenyl-2-(pyridin-4-yl)thiazole-5-carboxylate

This compound was made in a similar manner to ethyl 2,4-diphenylthiazole-5-carboxylate using ethyl 3-oxo-3-phenyl-2-(tosyloxy)propanoate and pyridine-4-carbothioamide (purchased from Aldrich). 1H NMR δ 8.76 (d, 1H), 7.90 (d, 1H), 7.83 (m, 4H), 7.48 (m, 3H), 4.33 (q, 2H), 1.32 (t, 3H).

Example 11 4-Phenyl-2-(pyridin-2-yl)thiazole-5-carboxylic acid

This compound was made in a similar fashion to 2,4-diphenylthiazole-5-carboxylic acid from ethyl 4-phenyl-2-(pyridin-2-yl)thiazole-5-carboxylate. 1H NMR δ 8.67 (d, 1H), 8.31 (d, 1H), 7.85 (m, 4H), 7.49 (m, 3H), 7.41 (dd, 1H).

Example 12 4-Phenyl-N-(2-(phenylamino)phenyl)-2-(pyridin-2-yl)thiazole-5-carboxamide

This compound was made in a similar fashion to N,4-diphenyl-2-(pyridin-3-yl)thiazole-5-carboxamide using 4-phenyl-2-(pyridin-2-yl)thiazole-5-carboxylic acid and N¹-phenylbenzene-1,2-diamine (Purchased from Aldrich). 1H NMR δ 8.65 (d, 1H), 8.23 (d, 1H), 8.08 (s, 2H), 7.80 (t, 1H), 7.70 (m, 2H), 7.47 (m, 3H), 7.39 (dd, 1H), 7.17 (t, 3H), 7.09 (m, 1H), 6.85 (t, 1H), 6.56 (d, 2H), 4.70 (s, 2H).

Example 13 Biological Assays of Certain Compounds of the Invention

The compounds of the invention were tested in various biological assays. The results of these assays indicated that the compounds of the invention ameliorated dysregulated bioenergetics and are, thus, useful for treatment of degenerative diseases and disorders, such as retinal damage.

MTT Assay

The compound 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) is a tetrazolium ion that is reduced to a blue formazan dye via several families of NAD(P)H-dependent oxidoreductases. Formation of the formazan dye from MTT or other related tetrazolium dyes are commonly used as a viability assay even though, in fact, the assay is a metabolic capacity assay. While it is true that dead cells can not produce NAD(P)H, very sick cells in the throes of death can exhibit extremely high levels of metabolic capacity as they attempt to overcome stress and it is well known that the MTT and related assays report on the ability of cells to produce reducing equivalents, and not live-dead ratios (Sumantran 2011). As shown below, it was found that the MTT assay was a useful metabolic assay when linked to more specific bioenergetic assays.

In this assay, 661W or C6 cells were maintained in DMEM supplemented with 10% FBS. 100 μl, of 70,000 cells/mL cells were seeded into each well of 96 well plates using DMEM supplemented with 5% FBS. Cells were then allowed to grow to confluency for 48 hours. The compounds of the invention were added in 2 μL media and calcium-ionophore A23187 was then added in 1 μL for a final concentration of 1 μM and after 24 h, 20 uL of 2 μg/mL MTT were added to each well and the cells were incubated for another 4 h after which 100 μL of 1% SDS in 0.01 M aqueous HCl were added to each well and the plates were incubated overnight. Absorbance was measured at 640 and 570 nM (background correction). The 1 μM ionophore A23187 caused about 50% loss in MTT signal at 24 h. Protection was calculated as the increase in absorbance of treatment groups normalized to the vehicle control. As shown in Table 1, the compounds of the invention gave significant protection at low concentrations:

TABLE 1 MTT Protection (%, Example No. concentration) 1 48%, 100 nM 2 40%, 100 nM 3 47%, 1 μM 4 64.1%, 100 nM 5 69%, 100 nM 6 78.4%, 100 nM 7 88%, 1 μM 8 67.3%, 800 pM 9 98%, 10 μM 10 88%, 500 nM 11 71.7%, 500 nM 12 57.2%, 800 pM

XF FCCP-Uncoupled Oxygen Consumption Rate Assay

The XF FCCP-uncoupled oxygen consumption rate assay assesses mitochondrial capacity by measuring cellular respiration. It was shown that the maximum FCCP-uncoupled oxygen consumption rate (OCR) was a good estimate of maximal mitochondrial capacity (Beeson 2010) and that IBMX treatment of 661W or C6 cells for 24 h caused a loss in maximal uncoupled OCR (Perron 2013). Thus, cells were pretreated with the exemplified compounds for 1 h, added 600 μM IBMX and then measured the uncoupled rate after 24 h. The OCR measurements were performed using a Seahorse Bioscience XF instrument (Seahorse Bioscience, Billerica, Md.), as previously published (Perron 2013). O₂ leakage through the plastic sides and bottom of the plate was accounted for using the AKOS algorithm in the XF software package. Cells were plated on 96- or 24-well custom plates designed for use in the XF and grown to confluency in DMEM+5% FBS (48 h). The medium was then replaced with DMEM+1% FBS for 24 h, along with any treatments. The IBMX treatment alone typically caused about a 50% decrease in the uncoupled rate and protection was calculated as the increase in absorbance of treatment groups normalized to the vehicle control. As shown in Table 2, below, the compounds of the invention gave significant protection in the concentration ranges that gave maximal protection in the MTT assay:

TABLE 2 XF FCCP OCR (% Ctrl, Example No. concentration) 1 71% @ 1 uM 2 77% @ 1 μM 3 72% @ 1 uM 4 83% @ 1 uM 5 82% @ 1 uM 6 81% @ 1 uM 7 75% @ 1 uM 8 73% @ 1 uM 9 71% @ 10 uM 10 70% @ 1 uM 11 76% @ 1 uM 12 71% @ 1 uM

As seen above, the compounds of the invention mitigate oxidative- and calcium-mediated loss of mitochondrial capacity in cell lines and protect photoreceptors from cell death in these models of retinal degeneration.

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It is to be understood that the invention is not limited to the particular embodiments of the invention described above, as variations of the particular embodiments may be made and still fall within the scope of the appended claims. 

What is claimed is:
 1. The compound according to formula (I):

wherein: R₁ is phenyl; R₂ is pyridinyl; R₃ is —NR₅R₆; and one of R₅ or R₆ is hydrogen or methyl and the other is lower alkyl substituted with alkoxy or phenyl substituted with halogen, alkoxy or —NH-phenyl; or a pharmaceutically acceptable salt thereof.
 2. The compound according to claim 1, wherein one of R₅ or R₆ is hydrogen and the other is lower alkyl substituted with alkoxy or phenyl substituted with halogen, alkoxy or —NH-phenyl.
 3. The compound according to claim 1, wherein one of R₅ or R₆ is lower alkyl and the other is lower alkyl substituted with alkoxy or phenyl substituted with halogen, alkoxy or —NH-phenyl.
 4. The compound according to claim 1, wherein R₃ is NH-halophenyl, —N(CH₃)CH₂CH₂OCH₃, —NH-phenylalkoxy or —NH-phenylaminophenyl.
 5. The compound according to claim 1, wherein said compound is 4-Phenyl-N-(2-(phenylamino)phenyl)-2-(pyridin-2-yl)thiazole-5-carboxamide.
 6. A pharmaceutical composition, comprising a therapeutically effective amount of a compound according to claim 1 or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier. 